The Battle of Kirin-do Island, was fought between the North Korean forces and the Mercenary. The Mercenary was deployed to Kirin-Do with the intent of destroying the Type-07 Supergun and verifying the Ace of Diamonds. After fighting through large amounts of NK forces, the Mercenary commandered the supergun, and destroyed it's counterpart across the canyon. Afterwards, the Mercenary tracked down and verified the Ace, who was trying to rally his forces. (Hint: as soon as you get off the Black Hawk, turn around and hijack it. It isn't protected from radiation, but will get you to the Supergun faster.)